1. Field of the Invention
The field of this invention is internal combustion engines and particularly such engines utilizing multiregional stratified air-fuel mixtures at the engine intake manifold and intake valve. Both spark ignition and compression ignition internal combustion engines are included.
2. Description of the Prior Art
Many spark ignition engines of the prior art have utilized stratified air-fuel mixtures at the engine intake manifold and/or intake valve (see for example references A, B, C, D, E, F, BB, CC, DD). In these prior art, spark ignition, stratified mixture, engines, two kinds of air-fuel mixtures are utilized differing in the ratio of air to fuel, and any one kind of air-fuel mixture is contained within a single continuous region and is not broken up into several small regions separated from one another by regions of another kind. As a result, whenever any portion of such a single continuous region is ignited by a spark, or any other ignition means, the entire region burns fully within a short time interval thereafter. This latter circumstance means compression ignition is impractical to use as a means of igniting these continuous regions, since compression ignition completes the burning of the entire region extremely quickly and strong pressure waves and an extremely loud engine noise are the consequence. Hence these prior art stratified mixture spark ignition engines can only use a spark or a flame from a spark for the ignition of the air-fuel mixture within the engine cylinder. As a result only those air-fuel mixtures which are spark ignitable or flame ignitable are used in these prior art stratified mixture engines. This type of engine intake stratification is hereinafter termed "two barrel carburetor stratification" since this is the most common manner of securing this type of stratification. In some cases of the prior art, in addition to one or two continuous air-fuel mixture zones as described above, an additional, continuous, air-only zone is also included in the stratified intake mixture. The term "two barrel carburetor stratification" is intended hereinafter to also include this type of intake stratification.
Experiments in engines show that air-fuel mixtures leaner in fuel than 24 lbs. of air per lb. of fuel cannot be spark ignited (see for example reference G) and that air-fuel mixtures leaner in fuel than about 27 lbs. of air per lb. of fuel cannot be flame ignited (see for example reference H). These then are the leanest mixtures useable in prior art, stratified mixture, spark ignition engines.
The use of very lean mixtures is desired in order to reduce the undesireable exhaust emissions of oxides of nitrogen. Experiments in engines show these emissions to decrease as air-fuel mixtures leaner in fuel are supplied to the engine (see for example references I and J). For prior art, stratified mixture, spark ignition engines, this beneficial effect of leaner mixtures to reduce oxides of nitrogen can only be utilized up to the flame or spark ignition limit of mixture ratio described above.
Extremely lean mixtures, at least as lean as 45 lbs. of air per lb. of fuel, can readily be compression ignited (see for example references K and L) and in this way greater reductions of exhaust emissions of oxides of nitrogen can be achieved than is possible with prior art, stratified mixture, spark ignition engines. When, however, compression ignition is used with air-fuel mixtures premixed according to the prior art in the engine intake manifold, strong pressure waves and in consequence unacceptably loud engine noise are produced (see for example reference M).
The diesel engine has long used compression ignition, and of very lean overall air-fuel ratio, without creating excess engine noise. Admittedley a diesel engine is commonly somewhat noisier than a spark ignition engine but is nowhere near as noisy as a prior art spark ignition engine in which a large continuous portion of the mixture is being compression ignited. The reason why the diesel engine can use compression ignition without excess noise must be sought in the manner of creating the air-fuel mixture which is then compression ignited.
In the diesel engine the air-fuel mixture is not created in the intake manifold but rather by injecting the liquid fuel into the already compressed air in the cylinder only a short time before ignition. As a result the air-fuel mixture which is compression ignited is stratified, in a particular way, since there is not enough time between injection and compression ignition for this liquid fuel to first evaporate and then diffuse fully into the surrounding air mass. The particular kind of stratification obtained in a diesel engine is hereinafter referred to as "injected liquid spray" type of stratification of an air-fuel mixture. This injected liquid spray kind of stratification is obtained when a liquid fuel is injected under high pressure into an air mass and atomized into many separate liquid drops. Fuel evaporates from each drop and diffuses gradually into the surrounding air and thus creates a zone of air-fuel mixture around each drop. Within each such zone a wide range of air-fuel ratios exists varying continuously all the way from very fuel rich next to the liquid surface of the drop, to very fuel lean fartherest away from the drop surface. The total number of fuel containing zones created is essentially equal to the number of liquid drops created by atomization. These many fuel containing zones are separate, discontinuous and essentially alike in having a wide range of air-fuel mixture ratios. In addition, one or more air-only zones may be created in those parts of the air mass into which no liquid fuel was injected. These evaporation and diffusion processes which create the injected liquid spray type of stratification are described in references N. O and P. An example of the use of this injected liquid spray type of stratification in the intake manifold of a spark ignition engine, rather than in the combustion chamber, is presented in reference EE.
An air-fuel vapor mixture can be ignited by compressing it adequately within a piston and cylinder chamber. Ignition does not occur immediately upon compression but only after a compression ignition time delay interval whose length varies with the degree of compression, the air-fuel ratio of the mixture, and the type of fuel in the mixture (see for example reference Q). In contrast to spark ignition, compression can be used to ignite air-fuel vapor mixtures of almost any air-fuel ratio provided only that adequate compression is applied. Hence extremely lean air-fuel mixtures can be compression ignited which could not be spark ignited. The burning process which occurs after an air-fuel mixture is compression ignited occurs with extreme rapidity as shown in reference R. The mechanism of this extremely rapid burning is a subject of controversy at this time but, if it does take place via the travel of a burning zone through the air-fuel mixture, then there is general agreement that the velocity of travel of this burning zone must be of the order or several thousands of feet per second, a velocity roughly ten times faster than that of the normal spark ignited flame. This extemely rapid burning and energy release from compression ignition creates strong gas pressure waves in the cylinder (see for example reference S) and, in consequence a very loud engine noise.
The diesel engine uses only compression ignition of an air-fuel mixture created by the injected liquid spray technique as described heretofore. The strong pressure waves, characteristic of compression ignition, are generated separately in each ignition region around each fuel droplet and, not being coordinated between regions, these several individual pressure waves occur at different times and travel in different directions and do not act together to increase engine noise. A consequence of this time and position dispersed occurence of compression ignition in the diesel engine is that this engine is much quieter running than is a compression ignition engine utilizing two barrel carburetor type of stratification at intake or homogeneous, premixed air-fuel mixtures. These latter engines are so noisy as to be unsuitable for any ordinary engine application. Hence we see that the combustion noise of compression ignition can be reduced to acceptable levels by having the compression ignition processes occur separately in individually small volume regions and at different times between regions.
In a diesel engine, after compression ignition has occurred the unevaporated liquid fuel portions and the over-rich-in-fuel portions, present in each region of the stratified air-fuel mixture, burn only with difficulty and some of these portions become soot which survives to exhaust in the form of exhaust smoke, an undesirable exhaust emmission of the diesel engine. The effects of fuel evaporating ability upon exhaust smoke emmissions of diesel engines is described in reference AA.
The most common type of spark ignition engine in use today, the gasoline engine, uses spark ignition in combination with a single barrel or two barrel carburetor for creating the air-fuel mixture. The resulting air-fuel mixture must be within the spark ignitability limits and in consequence engine torque is controlled by throttling the engine intake mixture. The result is a loss of engine efficiency due to the necessity of pumping out the exhaust gases at full atmospheric pressure. The magnitude and deleterious effects of this pumping loss are described in reference U. The normal flame, started by spark ignition, cannot reach all the way to the chilled surfaces of the combustion chamber and the thin film of air-fuel mixture next to the surfaces of the combustion chamber fails to burn fully and emerges as unburned hydrocarbon emmissions in the engine exhaust. Although these undesirable emmissions can be reduced by leaning out the air-fuel ratio, only limited improvements are available within the spark ignition inflammability limits. These surface film effects on hydrocarbon emissions are described in reference T and the effects thereon of air-fuel ratio are discussed in reference V. When the compression ratio of a gasoline engine is increased, in order to increase the efficiency of the engine, compression ignition of the last burning portions of the homogeneous air-fuel mixture may occur and the consequent locally rapid rate of pressure rise causes the undesirable noise known as knock. Although knock can be prevented by increasing the octane rating of the fuel being used such higher octane fuels are more difficult to prepare and thus are most costly to use. The compression ignition process of gasoline engine knock occurs in a single, moderate sized, region of essentially uniform and homogeneous air-fuel mixture and hence the pressure wave, characteristic of compression ignition, is a single, strong pressure wave which greatly increases engine noise.
In a spark ignition engine, whose air-fuel mixture is stratified at the time of combustion by containing some air-only regions or by containing some regions too lean for spark ignition, special ignition arrangements are sometimes needed to assure that spark ignition of the spark ignitable air-fuel mixture regions will take place at the proper time in the engine cycle. Various kinds of arrangements have been used in the prior art for this purpose including:
(1) Locating the spark plug in the combustion chamber at a place where a spark ignitable region of the stratified air-fuel mixture is also located. PA0 (2) Using a long duration spark discharge when the stratified air-fuel mixture is moving. PA0 (3) Using two or more spark plugs (multiple spark plugs) located at different places in the combustion chamber. PA0 (1) Engine exhaust emissions can be reduced by use of leaner air-fuel mixtures. PA0 (2) With spark ignition, air-fuel mixtures leaner than about 24 to 1 or at most 27 to 1 cannot be used as these are not spark ignitable. PA0 (3) With compression ignition air-fuel mixtures at least as lean as 45 to 1 and probably leaner can be used. PA0 (4) Compression ignition of a uniform air-fuel mixture produces excessive engine noise. PA0 (5) The noise of compression ignition can be reduced to acceptable levels by so stratifying the air-fuel mixture that small regions of air-fuel mixture are compression ignited at different times, producing a time and position dispersed occurrence of compression ignition. PA0 (6) Control of spark ignition engine power output by throttling the flow of the intake air-fuel mixture increases the engine friction power loss and hence reduces efficiency. PA0 (7) The spark ignitable portions of a stratified air-fuel mixture can be spark ignited by proper spark plug location, by use of multiple spark plugs, by use of long duration spark discharge or by a combination of these methods. PA0 (8) If the engine air-fuel mixture is stratified in the intake manifold, stratification is retained to the time of combustion. PA0 1. Supply a different fuel to each of several different regions, these several fuels differing in the kinds and proportions of hydrocarbons or other fuel components present. PA0 2. Supply a different fuel to each of several different regions, these several fuels differing in the amount or type of anti-knock compound present. PA0 3. Supply a different fuel to each of several different regions, these several fuels differing in the amount or type of proknock compound present. PA0 4. Furnish different proportions of air to fuel in the air-fuel mixtures in different regions. PA0 References:
To assure spark ignition of the spark ignitable regions requires only that a spark be present in the plug gap with the spark ignitable region also at the plug. In this way spark ignition of the spark ignitable regions can be secured by using one or a combination of the foregoing arrangements as is well known in the art.
That an air-fuel mixture, stratified in the engine intake manifold, will retain this stratification throughout the intake and compression processes, and thus be stratified at the time of combustion, has been shown in the "Background of the Invention" portions of the cross referenced related application and the references X, Y, Z as discussed therein.
In summary, the foregoing description of that portion of the internal combustion engine prior art, relevant to stratified intake mixtures, shows the following:
In the earlier cross referenced application a new kind of intake mixture stratification is described called "multiregional stratification" and is defined therein. The multiregional stratified intake charge of air and fuel, entering the engine cylinder on each intake process, consists of a large number of individual regions of air-fuel mixture. Each of these individual regions is of small volume, the weight ratio of air to fuel is essentially uniform throughout each region and the fuel type is essentially the same throughout each region. Adjacent regions differ in either the type of fuel or the air-fuel ratio or both. A stratified charge of air and fuel satisfying the foregoing requirements is hereinafter and in the claims referred to as a multiregional stratified air-fuel mixture or as an air-fuel mixture possessing multiregional stratification.
Use of such multiregional stratified intake mixtures in internal combustion engines makes available many beneficial objects as described and explained in the earlier cross referenced application. One of the beneficial objects made available by use of multiregional stratified engine intake mixtures is to permit the use of higher compression ratios and the consequent obtaining of higher efficiency from spark ignition engines without excess increase of noise. Higher engine supercharge can also be used to increase the power available from a given size of engine without excess increase of noise. Another beneficial object made available is to increase the part load efficiency of spark ignition engines by reducing the pumping work losses at intake. A further object is to reduce the quantities of undesirable smog generating materials, emitted via the engine exhaust, by making possible very lean mixture operation of the engine and by causing the combustion process to penetrate closer to the combustion chamber surfaces. For compression ignition engines a beneficial object made available is to reduce the quantities of unburned fuel, emitted as smoke, and thus to increase engine efficiency and reduce the emission of undesirable exhaust smoke. A further object is to provide a fueling method for compression ignition engines which is easier to construct and hence of lower cost than the fueling methods presently used for these engines.
One method of achieving certain of the beneficial objects made available by use of multiregional stratified intake mixtures consists in creating differences in the volumetric chemical energy content of the air-fuel mixtures in the various regions and in creating differences in the compression ignition time delay characteristic of the air-fuel mixtures in the various regions. Differences in volumetric chemical energy content can be created by setting different proportions of air to fuel in different regions. Differences in the compression ignition time delay characteristic of the air-fuel mixtures in different regions can be created in various ways already well known in the art such as:
When subsequently compressed, a multiregional stratified fuel-air mixture can be both spark ignited and compression ignited. Those regions which are compression ignited do so at different times during combustion and the resulting pressure waves are scattered and out of phase with each other. As a result less combustion noise is created than is obtained from the systematic gas vibration obtained when non-stratified air-fuel mixtures are brought to such high compression ratios that compression ignition occurs. Compression ignition of some of the regions produces locally strong pressure waves which, in reflecting off the combustion chamber surfaces, will carry the combustion process closer to the cold surface than is done by the normal spark ignited flame. As a result the thin layer of unburned or incompletely burned air-fuel mixture next to the cold combustion chamber surface, left behind after combustion is complete, is reduced and the smog generating materials originating in this unburned layer are also reduced. To reduce engine power output the number of regions in the multiregional stratified intake air-fuel mixture, which are leaner than chemically correct or which are air only regions can be increased thus reducing the chemical energy available and hence the engine power output. This method of controlling engine power output reduced the pumping work lost in pumping the intake charge into the engine and the exhaust charge out of the engine, when compared to the usual intake manifold throttling method of controlling the power output of spark ignition engines. As is well kown in the art, operation of a spark ignition engine at leaner air-fuel mixtures reduces the quantities of carbon monoxide and, if sufficiently lean, the oxides of nitrogen emitted via the engine exhaust. Hence the unusually lean mixture engine operation made possible by the use of multiregional stratification can reduce the quantities of undesirable carbon monoxide and oxides of nitrogen emitted by an engine. In an engine using compression ignition only, the devices of this invention premix the air and fuel with the fuel being fully evaporated before ignition, and thus less soot will be formed during combustion following ignition than is the case for the usual liquid injection method of supplying fuel to these engines. Liquid injection produces a poorly mixed and incompletely evaporated fuel-air mixture at the time of ignition and incomplete fuel burning results, producing soot and exhaust smoke and a reduction of engine efficiency. These problems of the usual liquid injection method of fuel supply can be largely avoided by use of multiregional stratified engine intake mixtures.
The only known prior art method of creating multiregional stratified intake mixtures for internal combustion engines is that described in the cross referenced related application. The devices of the cross referenced related application create a multiregional stratified air-fuel mixture by connecting a number of separate air-fuel mixing channels individually to a stratifier valve which connects in turn to the engine intake pipe. In each air-fuel mixing channel a particular type of air-fuel mixture is created by an air-fuel mixing device, such as a carburetor, followed by a heated section if needed to evaporate liquid fuel. The different channels produce different types of air-fuel mixture including an air only channel. These air-fuel mixtures may differ in the ratio of air to fuel and in the kind of fuel. The number of air-fuel mixing channels is equal to or greater than the number of different kinds of air-fuel mixture regions desired in the multiregional stratified air-fuel mixture at engine intake. The stratified valve contains at least one fixed port for each of the air-fuel mixing channels. These several fixed ports index with the moving ports of the moving element of the valve in a sequence to produce the desired pattern of differing regions of air-fuel mixture in the multiregional stratified air-fuel mixture passing from the stratifier valve to the engine intake pipe. During the intake process of the engine cylinder air-fuel mixture is drawn into the intake pipe from the moving ports of the moving element of the valve and thus from one set of fixed ports at a time as indexed by the moving ports, in a sequence of such sets of fixed ports repeated with each full cycle of movement of the moving element, and hence from that certain group of fixed ports and their connected air-fuel mixing channels which is composed of all the fixed ports in the several sets of fixed ports indexed by the moving ports. The moving element of the stratifier valve may be shifted relative to the fixed ports so that a different certain group of fixed ports is indexed and in consequence a different pattern of regions is produced in the multiregional stratified air-fuel mixture. Alternatively an adjustable mask may be interposed between the fixed ports and the moving element of the stratifier valve to make available the same capability of changing the pattern of the differing regions in the multiregional stratified air-fuel mixture. The principle, though not the only, reason for changing the pattern of regions is to change the engine power output. By increasing the proportion of leaner mixture regions or air only regions the power output of the engine may be decreased.
One disadvantage of the schemes used in the cross referenced related application to create the multiregional stratified engine intake mixture is that the stratifier valve is mechanically complex since engine torque is changed by changing the stratifier valve so as to index a different sequence of fixed ports within the valve.
Another disadvantage of the schemes used in the cross referenced related application to create the multiregional stratified engine intake mixture is that two or more different fuels are preferably used when a wide range of compression ignition time delay intervals is desired in order to reduce engine noise. Hence two or more fuel tanks and supply systems are then needed which increase the cost and complexity of the engine system. Additionally the use of two or more fuel tanks creates awkward refueling problems during engine use as, for example, when only one fuel tank has emptied.
The apparatus of this invention is used, in combination with an internal combustion engine, as a replacement for the torque control and air-fuel mixing equipment of said internal combustion engine and is connected to the intake port of said engine as described hereinafter, The term "internal combustion engine" is used hereinafter and in the claims to mean the known combinations comprising cylinders, cylinder heads, pistons operative within said cylinders and connected to a crankshaft via connecting rods, valves and valve actuating means or cylinder ports, lubrication system, cooling system, ignition system if needed, flywheels, starting system, fuel supply system, fuel-air mixing system, intake pipes and exhaust pipes, torque control system, etc. as necessary for the proper operation of said internal combustion engine. The term "internal combustion engine" is used hereinafter and in the claims to include also the known combinations as described above but wherein the cylinders, cylinder heads, pistons operative within said cylinders and connected to a crankshaft via connecting rods, valves an valve actuating means or cylinder ports, are replaced by a rotary engine mechanism combination, comprising a housing with a cavity therein, and plates to enclose the cavity, a rotor operative within said cavity and sealing off separate compartments within said cavity and connecting directly or by gears to an output shaft, ports in said housing for intake and exhaust. The term "internal combustion engine" as used herein includes atmospherically aspirated internal combustion engines as well as supercharged internal combustion engines using turbochargers or other types of intake air compressors.
A. Goosak et al, U.S. Pat. No. 3,283,751 PA1 B. Mallory, U.S. Pat. No. 2,156,665 PA1 C. Von Siggern, U.S. Pat. No. 3,418,981 PA1 D. Folcke, U.S. Pat. No. 3,170,445 PA1 E. Miller, U.S. Pat. No. 3,680,305 PA1 F. Dolza, U.S. Pat. No. 3,092,089 PA1 G. "Extension of the Lean Missfire Limit and Reduction of Exhaust Emissions of a Spark Ignited Engine by Modifications of the Ignition and Intake Systems," Messrs. Ryan, Lestz and Meyer, Soc. Auto. Engrs. Paper No. 740105. PA1 H. "An Evaluation of the Performance and Emissions of a CFR Engine Equipped With a Prechamber," Messrs. Wimmer and Lee, Soc. Auto. Engrs. Paper No. 730474. PA1 I. "A New Look at Nitrogen Oxides Formation In Internal Combustion Engines," Messrs. Eyzat and Guibet, Soc. Auto. Engrs. Paper No. 680124. PA1 J. "Influence of Engine Variables on Exhaust Oxides of Nitrogen Concentrations From a Multicylinder Engine," Messrs. Huls and Nickol, Soc. Auto. Engrs. Paper No. 670482. PA1 K. "A Study of Compression Ignition," B. Singh, MS in ME Thesis, Univ. of Wash., Seattle, Wash., 1965. PA1 L. "Some Factors Affecting Precombustion Reactions in Engines," Messrs. Corzilius, Diggs and Pastell, Soc. Auto. Engrs. Paper No. 852,1952. PA1 M. "A Detonation Wave Theory of Gasoline Engine Knock," Firey, Sixth Symposium (International) on Combustion, Reinhold, 1957, p 878. PA1 N. "The Ignition of Hydrocarbon Fuel Droplets In Air," G. M. Faeth and D. R. Olson, SAE Trans. 1968, Vol. 77, p 1793. PA1 O. "A Study of the Effect of Fuel Properties Upon Diesel Engine Combustion," J. C. Firey, MS Thesis, University of Wisconsin, 1941. PA1 P. "The Effects of Physical Factors on Ignition Delay," W. T. Lyn, E. Valdamis, SAE January Meeting 1968, Paper No. 680102. PA1 Q. "The Ignition of Fuels by Rapid Compression," C. F. Taylor, E. S. Taylor, J. C. Linengood, W. A. Russell, W. A. Leary, SAE Quarterly Trans., April 1950, Vol. 4, No. 2, p 232. PA1 R. "Photographs at 500,000 Frames per Second of Combustion and Detonation in a Reciprocating Engine," T. Male, Third Symposium on Combustion Flame and Explosion Phenomena, Williams and Wilkins, Co., 1949, p 721. PA1 S. "A Detonation Wave Theory of Gasoline Engine Knock," J. C. Firey, Sixth Symposium (International) on Combustion, Reinhold Co., 1957, p. 878. PA1 T. "Exhaust Gas Hydrocarbons--Genesis and Exodus," Daniels and Wentworth, SAE Technical Progress Series, Vol. 6. PA1 U. "Combustion Engine Processes," L. C. Lichty, McGraw Hill, 1967, p 334, p 405, p 490. PA1 V. "The Effects of Engine Operating and Design Variables on Exhaust Emissions," D. F. Hagen and G. W. Holiday, SAE March meeting, 1962, Paper No. 486 C. PA1 W. Barber et al, U.S. Pat. No. 2,484,009. PA1 X. "A Study of the Possible Effect of the Atkinson Cycle on Oxides of Nitrogen Emission from Gasoline Engines," Jinendrakumar Munot, M.S. in M.E. Thesis, University of Washington, Seattle, Wash., 1976. PA1 Y. Gau, U.S. Pat. No. 3,579,981. PA1 Z. "A Spark Ignition Engine with an In-Cylinder Thermal Reactor," Jessel, Uyehara and Myers, SAE paper number 730,634, 1973. PA1 AA. "Diesel Engine Exhaust Smoke: The Influence of Fuel Properties and the Effects of Using Barium Containing Fuel Additives," D. W. Golothan, SAE Trans., Vol. 76, p 616, 1967. PA1 BB. Cole, U.S. Pat. No. 1,537,748. PA1 CC. Burtnett, U.S. Pat. No. 1,481,955. PA1 DD. Burtnett, U.S. Pat. No. 1,546,007. PA1 EE. "Wetting the Appetite of Spark Ignition Engines for Lean Combustion," B. D. Peters and A. A. Quader, Soc. Auto. Engrs. Paper No. 780234.